1. Field of the Invention
The present invention relates to a plasma display device and a driving method thereof.
2. Description of the Related Art
A plasma display device is a flat panel display device that displays characters or images using plasma generated by gas discharge, and includes more than several hundreds of thousands to millions of discharge cells arranged in a matrix.
According to a method of driving the plasma display device, a frame is divided into a plurality of subfields, each having a reset period, an address period, and a sustain period according to variation in the operation over time.
In the reset period, the status of each cell is initialized so as to facilitate an addressing operation on the cell. In the address period, in order to select turn-on cells and turn-off cells, address voltages are applied to the turn-on cells (addressed cells) to accumulate wall charges. In the sustain period, sustain pulses are applied to the addressed cells to actually perform image display.
Generally, in the sustain period of the plasma display device, sustain pulses alternately having a high level voltage (in general, a Vs voltage) and a low level voltage (in general, 0 V) and having polarities opposite to each other are applied to scan electrodes and sustain electrodes, causing sustain discharge of discharge cells. In this case, a capacitive component formed by the sustain electrode and the scan electrode can be modeled as a panel capacitor Cp.
FIG. 1 is a schematic circuit diagram illustrating a driving circuit of a conventional scan electrode driver, and FIG. 2 is a block diagram schematically illustrating a scan electrode driving board and scan boards connected to the scan electrode driving board. FIG. 3 is a diagram schematically illustrating a sustain pulse applied to a scan electrode by the scan electrode driving unit shown in FIG. 1.
As shown in FIG. 1, a scan electrode driver 400′ includes a sustain drive unit 410, a reset drive unit 420, and a scan drive unit 430.
The sustain drive unit 410 includes a power recovery section 411 and sustain discharge switches Ys and Yg for forming a sustain discharge path. The switch Ys is connected between a power supply terminal Vs for supplying a Vs voltage and a scan electrode Y of a panel capacitor Cp, and the switch Yg is connected between a ground terminal for supplying a voltage of 0 V and the scan electrode Y of the panel capacitor Cp. The Vs voltage applied from the power supply terminal Vs through the switch Ys and the voltage of 0 V applied from the ground terminal GND through the switch Yg are alternately applied to the panel capacitor Cp.
During the sustain period, the sustain pulse is applied to the scan electrode Y of the panel capacitor Cp through each of a plurality of selection circuits 431 of the scan drive unit 430 by the operation of the switches Ys and Yg. In general, the plurality of selection circuits 431 are positioned in the form of integrated circuits IC (IC1 to IC12) on the scan boards 120 as shown in FIG. 2 and are connected to the panel capacitors Cp. Therefore, the sustain pulse actually applied to each panel capacitor Cp is affected by inductance depending on the distance between the sustain drive unit 410 positioned on the scan electrode driving board 110 and an output terminal of each of the selection circuits 431 (IC (IC1 to IC12)) positioned on the scan board 120. As a result, the sustain pulses applied through the selection circuits 431 (IC (IC1, IC2, IC11, and IC12)) furthest from the sustain drive unit 410 may overshoot as represented by a waveform C in FIG. 3. Further, the sustain pulses applied through the selection circuits 431 (IC3 to IC10) closer to the sustain drive unit 410 may overshoot as represented by a waveform A or a waveform B in FIG. 3.
As described above, when the voltages of the sustain pulses applied to the panel capacitors Cp are different from each other due to the difference in the distance between the sustain drive unit 410 and each selection circuit 431 (IC), a phenomenon may occur in which the upper and lower portions of the entire screen of the plasma display panel become brighter and the middle portion thereof becomes darker. Also, a phenomenon may occur in which the border lines between the portions of the screen corresponding to the selection circuits 431 (IC) are noticeable.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the present invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.